Presently, many mobile devices are equipped with sliding parts, such as sliding covers, that make it possible to expand the user interface surface of the device while still keeping the device compact in a closed configuration. The sliding part typically moves along rails installed in a base part of the device. Manufacturing such devices requires a high level of control over clearances between the rail parts. Ideally, the sliding part should be able to move freely without unnecessary friction between the rail parts, but at the same time any extra wobbliness between the parts is undesirable.
The challenge of controlling clearances between rails has been handled by tight control of tolerances in individual parts and the whole assembling process. This is challenging with slide mechanisms, in which distance between rails is large. In some devices the number of rails has been raised above two to counter wobbliness, but this adds cost and complexity to the device.